The difficulty in a terrestrial system is the inherent need for internal communication. Cells are generally not connected over the air. Instead, an air interface is defined within a small area around a base station (access radio port or microport). A number of microports are distributed geographically to give a desired region of coverage (e.g. the continental US). The distributed microports are connected by a plurality of access nodes to some core transport network, presumably wired, as opposed to wireless, as shown in FIG. 1. Several microports may be connected to a single access node.
Between access nodes, which are typically connected terrestrially over wirelines, an alternate means of addressing is needed. The demands of multimedia, for which terrestrial wireless systems are now being considered, imply transport by means of a fast packet switched network, e.g. ATM (Asynchronous Transfer Mode). Packet switching affords flexibility in the bandwidth assigned to a connection as well as in the delay incurred in propagating through the network. Message switching and circuit switching would not appear to offer the flexibility and speed necessary to meet the demands of multimedia. This is due, in part, to the longevity of message and circuit switched connections in a wireless environment, in which the users are mobile and move from cell to cell. Datagrams also do not appear to be a solution to the problems because of the additional circuitry and overhead involved in datagram reassembly. Both of the above observations further point to packet switching as a fast and flexible solution.
In current terrestrial CDMA wireless systems, user signals, received by an originating access radio port, are routed to the intended destination radio port using an individual spreading code to encode the signal. The individual spreading code uniquely associates the spread spectrum signal with a particular wireless receiver. This method reduces optimum system performance and data rates. Therefore, there is a need for a low-cost, flexible, high performance system that can distribute user data to the appropriate destination user without adding undue complexity and costs to the infrastructure (radio port) equipment. The present invention, as described herein, provides a low-cost, flexible, high performance means for interfacing a code division switched wireless system to fast packet switched network for backhaul to the core network.